164 • CHAPTER 6 Long-Term Memory: Structure
Later in our discussion of LTM, espe-
cially in Chapter 8, we will see how implicit
memory can lead to memory errors. We will
see, for example, that eyewitnesses to crimes
have identifi ed people as having been at the
crime scene not because they were actually
there, but because the eyewitnesses had
seen them somewhere else at another time,
so they seemed familiar.PROCEDURAL MEMORY
Procedural memory is also called skill
memory because it is memory for doing
things that usually require action. The
implicit nature of procedural memory has
been demonstrated in amnesia patients
who can master a skill without remem-
bering any of the practice that led to this
mastery (like the improvement in the pic-
ture completion task in Figure 6.11). For
example, H.M., whose amnesia was caused
by having his hippocampus removed (see
page 138), practiced a task called mirror
drawing, which involves copying a picture
that is seen in a mirror (● Figure 6.13). You can appreciate this task by doing the fol-
lowing demonstration.DEMONSTRATION Mirror Drawing
Draw a star like the one in Figure 6.13 on a piece of paper. Place a mirror or some other refl ec-
tive surface (some cell phone screens work) about an inch or two from the star, so that the
refl ection of the star is visible. Then, while looking at the refl ection, trace the outline of the star
on the paper (no fair looking at the actual drawing on the paper!). You will probably fi nd that the
task is diffi cult at fi rst, but becomes easier with practice.After a number of days of practice, H.M. became quite good at mirror drawing,
but each time he did it, he thought he was practicing it for the fi rst time. H.M.’s ability
to trace the star in the mirror, even though he couldn’t remember having done it before,
illustrates procedural memory.
Other amnesia patients also demonstrate procedural memory. Jimmy G. could still
tie his shoes, and Clive Wearing, who was a professional musician, was able to play the
piano. In fact, people who can’t form new long-term memories can still learn new skills.
K.C., who had lost his episodic memory because of a motorcycle accident (see page 158),
learned how to sort and stack books in the library after his injury. Even though he doesn’t
remember learning to do this, he can still do it, and his performance can improve with
practice. The fact that people with amnesia can retain skills from the past and learn
new ones has led to an approach to rehabilitating patients with amnesia by teaching
them tasks, such as sorting mail or repetitive computer-based tasks, that they can become
expert at, even though they can’t remember their training (Bolognani et al., 2000; Clare
& Jones, 2008).
We can also understand the implicit nature of procedural memory from our own
experience. We do not remember where or when we learned many of our basic skills;
nonetheless, we usually have little trouble doing them. Also, people can do things with-
out being consciously aware of how they do them. For example, can you explain how● (^) FIGURE 6.13 Mirror drawing. The task is to trace the outline of the star while
looking at its image in the mirror.
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